3. Consider the encryption scheme II in Question 2 and the experiment PrivKax, where adversary A is defined as follows: A outputs two messages m, = aab and m = abb. When given a challenge ciphertext c, A outputs 0 if the first two characters of c are the same, and outputs 1 otherwise. Questions: (a) Suppose Bob chooses b = 0. For what keys k will A succeed (i.e., A(m,,m,, Encz (m.))=0)? (b) Suppose Bob chooses b=1. For what keys k will A succeed (i.e., A(m,,m,, Ency (m))=1)? 2. Let II denote the Vigenere cipher where the message space consists of all 3-character strings (i.e., M = {a, ..., z}}), and the key is generated by first choosing the period tt, {1, 2, 3} and then letting the key be a uniform string of length t (i.e., kt, {a, ..., z}' or {O, ..., 25}'). So, the key space is K = {a, ..., Z} U{a, ..., Z}? U {a, ..., z}". Question : Compute Pr[K = k] for k = a, k = ab, and k = abc. 3. Consider the encryption scheme II in Question 2 and the experiment PrivKax, where adversary A is defined as follows: A outputs two messages m, = aab and m = abb. When given a challenge ciphertext c, A outputs 0 if the first two characters of c are the same, and outputs 1 otherwise. Questions: (a) Suppose Bob chooses b = 0. For what keys k will A succeed (i.e., A(m,,m,, Encz (m.))=0)? (b) Suppose Bob chooses b=1. For what keys k will A succeed (i.e., A(m,,m,, Ency (m))=1)? 2. Let II denote the Vigenere cipher where the message space consists of all 3-character strings (i.e., M = {a, ..., z}}), and the key is generated by first choosing the period tt, {1, 2, 3} and then letting the key be a uniform string of length t (i.e., kt, {a, ..., z}' or {O, ..., 25}'). So, the key space is K = {a, ..., Z} U{a, ..., Z}? U {a, ..., z}". Question : Compute Pr[K = k] for k = a, k = ab, and k = abc